Radio telegraphy and telephony.



J. H. HAMMOND, IR.

RADIO TELEGHAPHY AND TELEPHONY. APPLICATION HLED AUG.24. i912. RENEWED MAY [0' ms.

11,296,50%a iutvmed Man. 4, 1919 WITNESSES INVENTOR be produced by changing either the capo J'OHN HAYS HAMMOND, JR., 0]? GLOUCEsTER, MASSACHUSETTS.

RADIO TELEGRAPHY AND TELEPHQNY.

Specification of Letters Patent.

Patented Mar. 4. 1919.

Application filed August 24, 1912, Serial No. 716,864. Renewed May 10v 1918. Serial No. 233.790.

nscful Improvements in Radio Tcicgra'phy and 'lclephony, of which the following is a specification.

My invention relates to aystenis of radio tclcgraphy and tclcphony. and rclatcs more particularly to methods for periodically yaryin; thc amplitudc of transmittco clcctric wavcs.

hie-ans for acconipliishing this result have becn proposcd. but thcy arc limited to some form of pcriodit-al variation of the resistance at the transmittinc station. and, m reovcr. the rate oi ainplitudo variation is limited to freoucncim below the limits of audihility. It has boon shown that the variable resistant-c mcthod is an intcrior one for producino auiplitudc variations. mainly for tho rcason that a cilantro in rcsiatanco of say,

one per cent. will produce a change in tho rcct-ivcd currcnt intensity of vonly cqual.

valuc, or one pcr cont.

I Now it is well known in the art. of radio tclcgraphy that if a properly designed transinittcr and receiver are oila'illatiii gim rcs onancc. a changc' in wave length ofoi'rc-tenth of one pcr ccnt. of either transmitter or rcciyer will dcstroy the condition of resonance bctwecn thcm. The same 18 true in thc case of two tuned circuits of artranstnitting station or two tuncd circuits of a rccciying station. TlllS change in wave length may so that. for inatance. if a change of onc per cent. he made in cithcr the capacity or the inductance rot theitransmittey. a change of perhaps one hundred per cent. may be caused in the intensity of the received signals. It is also possible. by periodically varying the Capacity or the inductancc of the transmitting circuits. to produce a rccciycd impulsc of a sinusoidal character. Furthcrrnorc tho variations produced in thc transinitting apparatus hould preferably be of a Verypcaked form rathcr than of a 'more sinusoidal form. The rcason for this as I have found in expcrinicntal practice. that through the resistances of circuits there is a tendency for the wave form to be flattened out at the receiving station. and. therefore, in order to produce a true sinusoidal ware induct-.in-cc hetwccn coil l. and If.

- form at tho rccci ing station it is nccc sary to producc a very pcakcd wave form at tho transmitting station.

Referring to the accompanying drawings:

Figurc 1 shows transmitting apparatus with moans for arying the inductance of thc antenna circuit.

Fig. 2 shows transmitting apparatus with means for 'arying the mutual inductance between the antcnna circuit and the oscillation generator.

in. 1. a high-frcquciu-y alternator H impresses oscillations upon the antenna A by means or" the coils If and If. In circuit with the antenna A. arc the inductance coils L and S and the ground E. A rotary element R. iniyin polo picccs F; F, F andF composscd of iron or other magnctic substance. is in proximity to the coil S. so that where R is rotated. periodic variations are causcd in the inductance of S. and hence in tho inductancc of thc antcnna circuit. Thcsc variations in inductance will cause corresponding variations in the resonance betwccn thc antcnna circuit and the oscillaradiation of olcctric waves of periodically warring amplitude. the, periodicity of the 'by means of the coils L and L. The antcnna A is in circuit with inductance coil (i and lioliiitlctl at T1. The motor M is 'lliQUltttDEililf." onnectod to coil if. and can rotate thr lattor no a to alter the mutual .d'hcn motor Iii rotatcs coil if. pcriodic amplitude variations are thus caused in the electric wares radiated fronrA A rccci ing statio'n. with property tuncd'circuits, -will thcrc'iore rcspond to signals sent. from the corrosponding transmitting station. and a highly selective system of radio commuuication will thus he established.

I may usc thcr forms of oscillation goncrators. such. for instance. an an el'cctric arc.

.tion generator. and will thcrcfore cause the or I may use a timed closed ()S\?illfliiOI1 C ll can with a spark gap. and I niay (-niploy other appropriate-n1cans for varying thc indlictnln'c or tho capacity of either my antcnna circuit or-oi some other of my transmitting station circuits. Various other changes and nnnlifications, within the skill of those versed in the art, may be made in the particular apparatus shown and described herein, without departing from the spirit of my invention, providing the means set forth in the following claims be employed.

I claim as my invention 1 In a system of radio t'elegraphy and telephony, an antenna circuit, means for impressing high frequenc oscillations upon said antenna circuit, an -means for periodically varying the amplitude of said oscillations by varyingthe inductance of said antenna circuit in such a manner that the timeintensity curve shill be peaked.

9. In a radio system, the combination with means including an electrical induc ance for transmitting high. frequency waves, of means operative to vary the said inductance periodically and at a rate above the limits of audibility to imprcss amplitude variations upon said waves in such a manner that the time-intensity curve shall he peaked.

3. In a radio system, the combination with 'means including an electrical inductance for transmitting high frequency waves, of rotary means operative to vary the said inductance periodically and at a rate above they limits of audibility' to impress amplitude variations upon said waves in such a manner that the time-intensity curve shall be peaked.

4. In a radio system, the combination with means including an electrical inductance for transmitting high frequency waves, of ro-.

tary means including a plurality of pole piecesoperative-to vary the said inductance periodically to impress amplitude variations upon said waves.

5. In a radio system, the combination with means including an electrical inductance for transmitting high frequency waves, of rotary means including a plurality of equispaced pole pieces operative to vary the said inductance periodically to impress am plitude variations on said waves.

6. In a radio system, the combination with means including an electrical inductance for transmitting high frequency waves, of'lotary means including a plurality of radially arranged pole pieces operative to vary the said inductance periodically to impress amplitude variations on said waves.

7. In. a radio system, the c()1n:l irration with means including an electrical inductance for transmitting high frm uency waves, of ro tary means including equispaced radially arranged pole pieces operative to vary the said inductance periodically to impress amplitude variations on said Waves.

8 In a radio system, the (xm'ibination with means including an electrical inductance for transmitting high frequency waves, of to tary means including radial symmetrically arranged pole pieces operative to vary the said inductance periodically to impress anr plitude variations on said waves.

9. In a radio system, the combination with means including an electrical iiniiuctance for transmitting high frequency waves, of rotary means including a pole piece operative to vary the said inductance periodically to impress amplitude variations on said waves.

10. In a radio system, the combination With means including an electrical induct-ance for transmitting high frequency waves, of rotary means including a magnetic metallic clement spaced from said induc tanoe and rotatable with respect thereto about a fixed axis to vary the said induc tance periodically to impress amplitude v'ari'ations on said waves.

11. 'In a radio system, the combination with means including an electrical inductance for transmitting high frequency waves, of rotary means including an iron pole piece spaced from. and arranged to be rotated toward'and away from said inductance periodically to impress an'iplitude variations on said Waves.

This specification signed and witnessed this 15th day of August, A. 1)., 1912.

JOHN HAYS HAMMOND, Jn. Signed, in the presence of- Marian J. Coornn, S. A. TnonN'roN. 

